Suspension stability and mobility of Trap-Ox Fe-zeolites for in-situ nanoremediation

With Trap-Ox Fe-zeolites we intend to develop a novel nanoremediation concept, which is based on in situ trapping of organic contaminants by adsorption and catalytic oxidation in combination with oxidants such as hydrogen peroxide. Within this study, colloidal properties including surface charge and suspension stability as well as mobility in porous media were studied under various conditions for two Trap-Ox Fe-zeolite representatives: Fe-BEA35 and Fe-MFI120. These Fe-zeolites can act as adsorbent for contaminants and as micro-reactors for their catalytic Fenton-like oxidation. Both Fe-zeolites under investigation show remarkable suspension stability in slightly alkaline suspension (pH 8-8.5) without any additional stabilizers, but not in acidic suspensions (pH 5.5). Mobility investigations in columns with clean sand and natural sand suggest high mobility at slightly alkaline conditions. Particle breakthrough through 20 cm sand columns was > 75% for the two zeolites when injected as 10 g/L suspensions with a flow velocity of 10 m/d. However, under acidic conditions in natural sediment, a long period of near total deposition of particles is observed before high breakthrough occurs. The pH dependency is believed to be caused by charge inhomogeneity due to Fe-oxide clusters on the zeolites as well as on the sediment grains. (C) 2017 Elsevier Inc. All rights reserved.